Proceedings of The Fifth International Coral Reef Congress, 1985The Fifth International Coral Reef Symposium was conducted by The "Museum National d'Histoire Naturelle" (National Museum of Natural History) and the "Ecole Pratique des Hautes Etudes" (Practical School of Advanced Studies) in Tahiti, French Polynesia, from 27th May to 1st June, 1985.

About 600 participants registered at the symposium, representing 44 countries. Approximately 400 papers were presented and 208 papers were published in 6 volumes proceedings of the symposium.

Global metabolic activity of two Caulerpa of TAKAPOTO lagoon: Caulerpa urvilliana Montagne and
Caulerpa bikiniensis Taylor have been measured.!!!. ~ by incubation in respirometer system with oxygen
probe.
Net ~hotosynthesis (y) in mg 02 .g-1 .h-l as a function of light intensity (x) in E/m2 .h is:
y = 2.4 x -1.13 at -2 m, and y = 6.2 x -1.13 at -10 m for Caulerpa urvilliana Montagne and y = 36.6 x
-2.18 at -26 m for Caulerpa bikiniensis Taylor.
Comparison of these results with value of surface light intensities and irradiance profile at
different depths gave us an estimation of the organic matter turn-over: 35 and 23 days for Caulerpa
urvilliana Montagne at -2 m and -10 m, and 19 days for Caulerpa bikiniensisTaylor at -26 m.

The symbiotic dinoflagellates isolated from the jellyfish Cassiopeia and the anemone
Condylactis were described as Symbiodinium microadriaticum Freudenthal, 1962. Since that time, the
tendency among investigators of symbioses involving algae that superficially conformed to descriptions
of S. microadriaticum has been to regard all such algal symbionts as being conspecific, regardless of
their geographic origins or the invertebrate hosts with which they associate. More recently, a variety
of independent studies have uncovered stable and fundamental differences among the algae called S.
microadriaticum originating from different host invertebrates from the Atlantic and the Indo-Pacific.
Differences in isoenzymes, sterol ccxnposition, form and structure of the light-harvesting
peridinin-chlorophyll ~-protein complexes, morphology, infectivity, circadian rhythmicity of motility
and photoadaptive physiology have been documented. The observed differences, though strongly
suggestive, did not provide conclusive evidence that the different algal populations represented
different species, so they have been regarded as different strains within the same species. Resolution
of the species problem has been hampered by a lack of genetic evidence.
We have now conducted morphometric studies on the nuclei and chromosomes of S. microadriaticum
isolated from the jellyfish Cassiopeia xamachana, the anemone Heteractis ~- (both from the
Caribbean), the anemone Anthopleura elegantissima and the coral Montipora verrucosa (both from the
Pacific). The analyses were based on three-dimensional reconstruction of nuclei after ultra-thin
serial sectioning and electron microscopy.
The data show that the different algal isolates possess different chromosome numbers and
different chromosome and nuclear volumes. The simplest explanation for the observations is that, if -
continue to regard the algae from Cassiopeia as ~. microadriaticum as the rules of taxonomy would
dictate, then the other algae represent different species. The differences in chromosome numbers and
volumes suggest a strong likelihood of severe cytogenetic problems should these algae exchange genetic
materials during sexual reccxnbination. All the differences observed, when taken together, are
consistent with the algae being different species in the context of the evolutionary species concept.

An ecological survey was undertaken in five coral reefs around Yucatan (Arcas Arenas
Triangulos, Alacranes and Chinchorro). Nutrients were measured at the water column and the ben~hos wa~
sampled by point quarter method. There were no significant changes in water quality in and out of each
coral reef; however, at the southernllk>st part of Chinchorro Bank, the N:P ratio suggests an upwelling
nearby. Two out of the five coral reefs studied (Alacran and Chinchorro) show a well formed lagoon as
well as the highest development and habitat diversity. Data analysis leads to the interpreation
according to which the ridge growth rate is not the same in all places. In the evolution of these
coral reef cannunities, the ridge growth is very important at the east and southeast margins with
Acropora palmata as the most active element at the uppermost level which often reaches the sea surface;
further on there is a slope (spur and groove characteristics) where calcareous algae grows actively,
sharing the biotope with Millepora complanata, Gorgonia flabellum and Agaricia agaricites. The slope
leads to a terrace at 15 to 25m. The!. palmata and calcareous algal growth is passive at the reef
margins on the north, west and south sides and Montastrea annularis, Gorgonia flabellum, Agaricia
agaricites and Briareum asbestinum are the dominant species of the community. On these margins the
formation of ridges is unusual, there are no spurs and grooves and the terrace may not be well defined.
The lagoons are usually formed as a consequence of a scarce coral growth in protected areas playing role as deposits of sediments released on the east ridges. Cayo Arcas which holds an oil punping
station has been subjected to considerable environmental stress, which is reflected in the biota. It
offers a potenti~l for IIk>nitoring how reefs are affected by these human activities.

Of the net carbon fixed daily by zooxanthellae in the Red Sea coral Stylophora pistillata,
more than 95% is translocated to the host animal tissue. Of that amount, a fraction is respired by the
animal, satisfying 100% of its maintenance respiration needs. The remainder is potentially available
for assimilation. The percent contribution of this fraction to animal growth is not easily canputed
because of the difficulty of measuring coral animal tissue growth rates. From a large data set on mean
geometric radius of~. pistillata vs. time, we established corresponding surface areas v. time, and
knowing the standing stock of animal tissue per unit surface area, were able to calculate the specific
growth rate of animal tissue. From these data, the contribution of translocated carbon to animal
growth was calculated. Values will be presented and their implications with respect to zooxanthellae
expulsion, digestion, and other losses from corals will be discussed.

A microcomputer-controlled underwater apparatus was designed and utilized to continuously
monitor photosynthetically active radiation and daily oxygen flux in marine photoautotrophic
organisms. The respirometer employs precision polarographic dissolved oxygen probes, a semi-closed
flushing system, and a microcanputer data acquisition system which also controls flushing frequency.
Four organisms can be monitored simulataneously, each in an optically pure quartz glass respiration
chamber. The apparatus is 12 volt DC powered and can be used in a stand alone mode for up to 26
hours. When connected by hardwire to another microcomputer at the surface, the system can be left ~
situ for several weeks, and in this mode, continuous monitoring of the experiments is possible.
-The respirometer consists of three separate housing modules --to facilitate deployment in the
field and minimize potential damage in the event of flooding --and is constructed of
corrosion-resistant alwninwn, stainless steel, and 1exan. t-k>lded rubber watertight electrical
connections are used, and p1wnbing is machined within the housing walls. Most of the operational
canponents are can~rcially obtained and unmodified; consequently repair and rep1ace~nt is
simplified. The electronics are dependable and programmable, permitting remarkable flexibility in
experiment design. Three respiration chamber sizes permit a variety of experi~nta1 organisms to be
tested. The system was designed and used expressly for monitoring productivity and respiration in
symbiotic Cnidarians, but is suitable for other marine ol"ganisms.
Details of construction and schematics are provided, together with suggestions for possible
modification and adaptation of the system.

Qatar is a peninsula on the western side of the Arabian Gulf. The bottom of the eastern coast
of Qatar consists of sand, shells and gravels interspaced with coral reefs. Eight species of coral have
been identified in the Qatari waters, namely Acropora, Platygyra sp. (very common), Montipora sp.,
Pavona sp., Porites sp., Favia sp., Psammocora sp., Turbinaria sp. Oxygen, pH and nutrients were
studied in Qatari wate-r-;-d-;:;-ring winter and summer seasons of 1983-1984. The study showed a higher than
average concentration of oxygen, inorganic nitrogen, silicate during winter than that of summer, while
phosphate revealed a reverse trend. Compared to the off-shore waters, high concentrations of nitrate
and nitrite were observed at the coral reef areas in the south eastern part of Qatar coast during the
summer season.
The calculated atomic ratio of P:N:Si showed values fluctuating from 1:3.8:40.8 during winter
to 1:1.7:16.4 during the sunmer season. A high N:P ratio was found particularly in areas of coral reefs.

The variations of the magnetic field on an atoll surface (Clipperton Island, almost-atoll),
point out the setting, spreading and deepness of volcanic masses in a coral accunulation md Uk>re
precisely at Clipperton, the presence in deepness of magnetic and volcanic masses greater than the
trachyte outcrop.

The coral reefs of Madagascar, located in particular on the west coast, extend for a total
length of IIPre than a thousand kilo~tres. Their lagoon or post-reef channel is used as a means of
communication. At Nosy Be and Tolaria, the reefs attract a large number of tourists. The massive
madreporites, such as Porites somaliensis, are sometimes used as building blocks or as slag for
drains. In certain areas broken shells of large size are used to make quicklime. Certain species of
edible algae can be cultured (genus Eucheuma); and some molluscs are used as a source of food. These
include gasteropods of the genera Fasciolaria, ~ and~; the bivalves Gafrarium pectinatum and
Meleagrina margaritifera. ~ marmoratus and ~ margaritifera are particularly sort after for their
mother-of-pearl, and Cypraeacassis ~ for the manufacture of cameos in Europe. Amongst the molluscs
the cephalopods, Octopus and ~ are fished for local consumption or export. Amongst the crustacea,
small shrimps are fished and occasionally the lobster Panulirus pencillatus. The common echinoid,
Tripneustes gratilla is taken for its gonads. The holothurians (Holothuria scabra, Holothuria
tubulosa, Thelenota ananas) are of concern to Asiatic countries which exported from 5 tonnes (1982) to
56 tonnes (1981). Fi"Sh are also taken for local consunption and for export. The marine turtles,
Eretmochelys imbricata, Chelonia~, are similarly hunted. Thus, coral reefs playa role in
socio-economic activities of some countries as the canll11nities they support provide the human
population with a source of food, aswell as economic and industrial resources of some importance.

Twenty-six Permian limestone blocks, from 17 localities in the Glass Mountains, west Texas,
were acid-etched to reveal silicified bryozoan patch reef-thickets <1 m high. These small Wolfcampian
and Leonardian bioherms, located basinward below the larger reefal banks rimming the Permian Basin,
consist of dense tangles of fragile silicified bryozoar. colonies, infi11ed partly with skeletal
carbonate sands. The bryozoans are highly diversified, approximately 80 species, in contrast to
contemporaneous cratonic-shelf faunas, but only a few carried out the bulk of the reef construction.
In most of the reef-thickets, pinnate Acanthoc1adia zoaria grew up closely spaced, with their branches
intertwining around one another, snd often directly touching each other. Above the acanthoc1ad bases,
fan-like fenestrates --especially Po1ypora, Mini1ya ("Feneste11a") , Septopora, Protoretepora and
Anastomopora --attached to the acanthoc1ad branches, and also to one another in a nested fashion.
Locally, encrusting fistu1iporoids, ribbon-like bifo1iates, cylindrical rhanboporoids, delicate
pennireteporids, ramose trepostomes, bead-like ca1cisponges, and isolated brachiopods are scattered
within the acsnthoc1ad-fenestrate frame~rk. The bryozoan colonies thus collectively built a
framework, specifically a branchstone, which also served to trap or baffle fine sediments within its
interstices, and hence could also be classified as a baff1estone where the brsnches are more widely
spearated; Some of the fine sediment appears to be comminuted bryozoan debris. In many of the upper
Leonardian reef-thickets, branching trepostomes (Tabu1ipora?) replaced the acanthoc1ads, filled their
role in frame-building snd sedi~nt-trapping, snd so produced a more robust frame~rk than the earlier
reef-thickets.

Extensive reef coral zooxanthellae expulsion occurred from Key Largo to Dry Tortugas, Florida,
during September 1983. Coral bleaching was intensive between Pelican Shoal and Sand Key Reef off Key
West. Coral discoloration extended to depths exceeding 14 m but was especially severe in shallow (1-2
m) spur and groove habitats. Approximately 75-957. of all Millepora complanata and Palythoa caribaeorum
were bone white, but most colonies remained viable. Affected~. complanata (bladed fire coral)
retained the ability to inflict pain from dactylzooid nenatocysts. Some individuals (5 to 107.) had
fine algal growth indicating death on all or parts of their skeletons. Although 15 species of
cnidarians, principally Scleractinia, were affected, some species (Madracis mirabilis, Porites porites,
Montastraea cavernosa, Dendrogyra cylindrus) appeard to be immune. A quantitative sample at Eastern
Sambo Reef on 6 October documented 11 species and 209 colonies;~. complanata comprised 32.57. of all
colonies. Transmission electronmicrographs did not reveal epidemic pathogenic organisms in affected
coral tissues. Warm, calm weather prior to the expulsion was conducive to elevated seawater
temperature. A seawater thermograph deployed off Marquesas Key recorded temperatures of 32.3.C during
the period.
A seven month post-event survey revealed that most hermatypic organisms had recovered normal
color. Survival of hermatypic cnidarians was high. Twenty quadrats sampled during and seven months
after the event were compared using classification analysis (Czekanowski's quantitative coefficient);
mean similarity value among all quadrats was 0.69, and 12 of 20 quadrats had similarity values> 0.70.
Values obtained using this technique in similar habitats generally ranged from .4 to .9 annually. The
event is an example of a disturbance of intermediate frequency and magnitude controlling shallow reef
canmJnities.

A major component of the soft coral assemblages on outershelf and midshelf reefs off
Townsville, central Great Barrier Reef region, is the genus Efflatounaria. This xeniid soft coral
propagates vegetatively by means of stolons which give rise to daughter colonies.
Subpopulations of an Efflatounaria species were studied between December 1980 and June 1982 at
two sites at Davies Reef (18°50'S, 147°39'E), one site having overall a comparatively higher density of
Efflatounaria than the other site. Using maps derived principally from stereophotographs taken at
approximately two-monthly intervals, rates of natalit2 (i.e. production of new colonies) and mortality,
and changes in relative abundance, were followed in 1 m plots at 5m and at 10m below l.w.d. (at both
sites), and at high and low densities of colonies within plots (at Site 1 only).
Vegetative propagation was observed year-round irrespective of sexual reproductive activity,
ne.l autonomous daughter colonies being produced within periods of less than two months. Three-way
ANOVAs of standardized natality and mortality data indicated, ~~, a significant effect of
density on both natality and mortality rates. This suggests that the species' potential for rapid
population increase is not realized, the higher natality rates at high densities being offset by higher
mortality rates.
Efflatounaria sp. is dioecious. Release of eggs occurs in early summer (observed early
Decsnber), and is not fully synchronous but is epidemic over a period of a few days. Following
release, eggs remain attached to the colony exterior between the swollen polyps, and planulae are
probably brooded here. Most propagules of this Efflatounaria species appear to be produced
vegetatively, and it seems likely that sexual reproduction serves primari ly to promote dispersal, and
maintenance of genetic diversity.

Intraspecific variability is currently being assessed for a patch reef population of a
dominant hermatypic coral, Porites compressa, in Kaneohe Bay, Hawaii. Clonemates are distinguishable
fran allogeneic colonies based on corallum morphology and color. ImllUnocanpatibility testing by
grafting, and preliminary electrophoretic analyses have provided corroboration of genetic identity for
colonies representing seven morpho types. In aldition, each morpho type is unique in its total
composition and/or relative proportions of a suite of UV-absorbing compounds. Samples from 37 colonies
produced chranatographic signatures characteristic of their particular morpho types. Variation in
UV-absorbing compounds in this species provides a new method by which individual colonies can be
assigned to different clonal groups.
Single colonies tend to dominate large areas (up to 15 m2), especially on the seaward side of the patch
reef. Even in the most clonally diverse (leeward) areas of the reef, 40.,. of the total coral cover is
comprised on only three morphotypes, represented by 91 separate colonies. Asexual (clonal)
reproduction, followed by colonization and success due to temporal precedence or competitive
superiority, seems to be an important aspect affecting the population structure of this species.

This study is based on images of the Landsat 3 satellite and on continuous bathymetric records
carried out by the author, as a field control, in the lagoons of the Gambier Islands and of the atolls
of Takapoto, Rangiroa, and Temoe, in the Tuamotus. Correlations are established between the water
depths and the digital values recorded by Landsat, making possible a detailed canputer bathYlretric
mapping of shallow coral reefs. This enables us not only to test the accuracy of available charts, but
also to successfully map, at very low cost, sane hitherto uncharted areas, such as the northern part of
the Gambier Lagoon, the lagoon of Temoe, and the "Portland Banc", which is in fact a submerged atoll.
In the lagoon of Takapoto, on the other hand, mapping has been less successful, the weak
transparency of the water often preventing the satellite from "seeing" the bottom of the lagoon. In
Rangiroa, where water transparency lessens as the distance from the two passes increases, the relation
between radiance and water depth changes, thus making it necessary to carry out more field
verifications and to map separately various parts of the lagoon.
Lastly, the best results have been obtained in Temoe Atoll, where the bottom of the lagoon is
"seen" everywhere by the satellite, thus enabling a canplete mapping of all the lagoon and an
evaluation of its volume.
In conclusion, the resolution of Landsat is not best adapted to the coral reef environment and
local water depths can only be evaluated by taking into account rather high confidence intervals. With
the Spot satellite however, one may expect an obvious improvement in marine charts where the water is
transparent, the sky cloudless and t:he water depth less than twenty lretres.

During several field trips in French Polynesia, ten species of algae belonging to the genus
Halimeda (Caulerpales, Udoteaceae) were found: Halimeda disco idea, ~ gracilis*, H.incrass4ta f.
incrassata, H. incrassata f. ovata, H. lacunalis*, H. macroloba, H. micronesica*, H. minima*, H.
opuntia, H. simulans, H. taenicola:-FOur of them (*) were found for the first time in this region of
the South Pacific.
The description and distribution of all these taxa is given. The distribution of these
Halimeda in French Polynesia shows marked differences in vegetation from one island to another.

The Black Band Disease (BBD), caused by the cyanophyte Phormidium corallyticum, was previously
known mainly from Caribbean Scleractinia. The behavior of the disease on some of the Western Atlantic
stony corals is reasonably well understood.
Occurrence of BBD in the Indo-Pacific was reported very recently, and the identity of the
disease is confirmed here. Species of the genera Platygyra, Leptoria, Goniastrea, and Hydnophora were
found to be the most susceptible to BBD, also showing the fastest progress of the disease. Many
Indo-Pacific species seem to be at least resistant, others, especially of the genus Acropora, proved to
be immune to BBD.
As has been shown for Caribbean reef corals, an acute White Band Disease (WBD) was found to be
the most canmon natural starting point for a BBD on susceptible Indo-Pacific species as well. However,
in both zoogeographic regions BBD was also observed to establish itself in injuries caused by
interspecific aggression among Scleractinia. Both, WBD and the extracoelenteric feeding by mesenterial
filaments are biochemical processes and result in progressive lysis of the afflicted coral tissue.
These, or similar conditions, may be a prerequisite for BBD, while physical injuries of various kinds
do not seem to promote infection with BBD.
Phormidium corallyticum, also causes genuine BBD on Caribbean Gorgonia and can be found
occurring naturally on sea-fans in the West Indies. Proof of the pathogen's identity was obtained by
microscopic examination as well as by repeated artificial cross-infection with susceptible
Scleractinia. Similar infection experiments on several soft and horny corals of the Red Sea proved to
be unsuccessful. To date, no Indo-Pacific octocorals were found afflicted with BBD in nature.

The dendronotid nudibranchs Melibe ~ and an unyescribed Melibe sp. showed significant ratis
of photosynthetic C fixation (5850 pg C mg. chlorophyll ~- ~- and 3290 pg C, mg. chlorophyll ~
-h-1,respectively) due to symbiotic zooxanigellae. Dark 4C fixation was <4.57. of the light rate.
DCMU caused similar inhibition of photoi4nthetic C fixation in Melibe sp.
Melibe sp. accumulated 50-56% C in structural tissue/p~s compared with 37-43% in Melibe
14 pilosa. A similar amount y£ C per unit chlorophyll ~ was entrained in lipids and intermediary
metabolites in both species. C incorporated into lipid was found predominaniky in triacylglycerides
(42-72%) and charged lipids (22-42%) with M. ~ showing slightly greater C incorporation into the
former. 14c was not incorporated into lipids -;hen photosynthesis was inhibited by constant dark or DCMU.
ExaTlnation of host tissue and zooxanthellar fractions indicated that, in the light, 457. of
the fixed C in Melibe sp. and 377. in ~ ~ was translocated to the host tissues.
Zooxanthellae-free egg masses produced by Melibe sp. during a 60 h "cold-chase" period contained
considerable amounts of photosynthetically-fj;;JJ14C.
Data are discussed in terms of carbon fixation and partitioning, translocation, and lipid
synthesis in nudibranch and other zooxanthellar symbioses.

Numerous small carbonate platforms are present in the Jubal Strait where the southern Gulf of
Suez merges with the northern Red Sea. The Ashrafi reef canplex, t~ small platforms along the -stern
side of the strait, was the focus of marine geology and physical oceanography studies. These features
are evolving in an active marine environment that is operating within the geological constraints of
large, complex graben with mountainous fault-controlled margins. Substrate for the platforms is
uncertain, but a fault-controlled initial stage is likely. Regardless of origin, ouch of the present
streamlined morphology appears to be a product of sediment transport driven by strong rectilinear tidal
currents (", 50 cm/sec), which dominate exchange processes in the strait. Surface winds that bl~
consistently from the north (down the Gulf axis) augment southerly flowing currents by 5-10 cm/s.
The streamlined shapes of the Ashrafi platforms are products of wave-stioulated reef accretion
on the northern ends and downdrift sedimentation to the south. Sediment transport/deposition is forced
by strong tidal currents coupled with unidirectional wind drift from the north. Sediment transport
along the platform flanks is augmented by intense burrowing activity of Callianassa through bioejection
of particles into the water colunn during the mound-building process.
High salinities develop on the shallow platform tops (measured at ~ 47%0). A lack of coral
growth, abundant large plus porcelaneous foraminifera and near total exclusion of sediment-producing
calcareous green algae may be related to these hypersaline conditions.

Predation and competition play key roles in the structuring of coral reef communities.
Studies of terrestrial systems have shown that predation and canpetition are often chemically mediated
or influenced. The complexity and importance of chemical interactions are perhaps best known form
terrestrial plant-herbivore investigations. Chemical interactions appear to be equally important in
coral reef ecosystems.
The potential of a chemical approach to coral reef ecology can be illustrated by a specific
example: the ecological implications of prostaglandin production in the Caribbean gorgonian Plexaura
homomalla. This organism contains prostaglandin A2 --a fatty acid derivative with potent,
hormone-like activity --in concentrations 10 million times higher than those of other animals.
Prostaglandin A2 induces severe vomiting in fish, and appears to be a defensive poison in P.
homomalla. Fish quickly learn to avoid food pellets containing prostaglandin A2. The gorgonian-eati~
snail Cyphoma gibbosum, however, grazes with impunity on ~ homomalla. Preliminary observations
suggest that £. gibbosum contains distasteful cOmpounds, which may be derived from the gorgonians on
which it feeds. The conspicuous coloration and gregarious behaviour of ~ gibbosum may be adaptations
which increase the selective advantage derived from distastefulness.
Further research into the chemical ecology of coral reefs should provide new insight into the
mechanisms which structure this unique, diverse habitat.

An analysis and interpretation of the reef community structure and petrographic variation
within an emergent Holocene limestone on Guam are presented. The Merizo limestone, a former
flourishing coral-algal reef complex now elevated up to 2.0 meters above present sea level, was studied
at extensive outcrops at Aga Point on south Guam. Two distinct coral canlTllnities are apparent: a
low-diversity (Shannon-Weiner D = 1.96), Pocillopora-Acropora-rich, high-energy seaward facies and a
high-diversity (D = 3.30), Porites-Heliopora-Stylophora-Montipora-Platygyra-rich, low-energy, landward
facies. Coral coverage varies from 35 to over 407., seaward versus 20-307., landward. The ranaining
volumetrically significant reef components are laminated red algae (5-137.) and tan, variegated
biomicrite-biomicrudite (50-707.) detrital limestone. Although the levels of diagenetic changes are
relatively minor, petrographic analysis (supported by SEM-EDX and XRD) indicates at least five styles
have over-printed earlier fabrics. In paragenetic sequence those styles are: (1) isopachous rim
cements; (2) micrite and peloidal micrite aggregation in body cavities and as intergranular cement
within detrital limestones; (3) terrigenous and bioclastic infill of very-fine sand to fine silt clasts
incorporated within colloidal size iron and aluminum-rich micrite; (4) neomorphism, as micrite
enlargement to microspar; (5) pisolitization of random clasts within detrital limestone. The
chronology suggests a continuation from submarine diagenesis during Holocene reef-forming time through
freshwater mixing with introduction of terrigenous canponents to on-going post-emergent vadose
processes. Comparison of the Aga Point with other Merizo localities shows similar trends in community
structure relationships but different diagenetic changes, both in variety and intensity. Based on our
analysis, the Merizo appears to have a split personality; the coral community structure and mesoscopic
variation are a response to geomorphic features that pre-date the post-Wisconsin transgression;
however, at microscopic levels of resolution, the evidence suggests a continuing and on-going evolution
in the lithology of the Merizo limestone.

Scleractinian corals investigated in Australia and Hawaii all exhibited a similar pattern of
external development. In all species, eerly cleavages occurred usually every 60 minutes or less. Such
externally developing coral embryos provide a source of rapidly dividing cells which enabled good
chromosome preparations to be made. Detailed ~thods and suggested modifications of technique are
discussed. The karyotype of 4 species, representing 3 families, is presented. Preliminary results
suggest that karyotypic data will be useful for higher level systanatics. The use of externally
developing coral embryos has application to the majority of coral species and opens the way for
extensive cytogenetic investigation of the Anthozoa.

The purpose of this paper is to compare, with the help of sea charts, selected submarine and
aerial photographs, two of the most developed barrier reefs in the ~r1d: the New Caledonian barrier
reef (South-west Pacific), parallel to the two coasts of the island from 18 to 23° South latitude, over
a length of 1500 km, and the Mayotte barrier reef (Comoro Archipelago, Western Indian Ocean), 150 Ian
long, which surrounds the volcanic island between 12°30 and 13° South latitude.
Major morphological features of the two coral reef canp1exes are investigated with respect to
geological criteria (lithology, age, structure of the two islands) and regional climatic data. The
features studied include: bathymetry of the lagoons, outer and inner slopes; distrit.Jtion, shape, size
of the organic build-ups and detrital accumulations.
Many similarities are pointed out such as depth of the passes, presence of a submarine river
pattern and a partly karstic topography, showing the important and general role played by the eustat~c
sea-level falls in the morphology of reef canp1exes. Likewise, the existence in the two areas of
pieces of submerged barriers or inner barriers attests the importance of the local tectonic control.
Nevertheless differences appear, among others, lack of emerged reefs in Mayotte (except reef
debris associated with volcanic eruptions) meaning the regional geodynamic evolution is less complex
than in the South-western Pacific; scarceness and immaturity of s8-'1d cays c~pared with those of N~
Caledonia, due to different hydrodynamic conditions Last1y,the New Caledonia model, better known because of many borings Which perforate it, is
used to propose some hypothesis about the age and deep structure of the Mayotte barrier reef.

Middle Paleozoic algal and coral-stromatoporoid reef complexes in Alaska represent unique and
divergent examples of carbonate shelf margin systems both sedimentologically and paleoecologically.
The algal reef complex, Late Silurian-Early Devonian in age, is exposed in southwestern Alaska within
the Holitna Basin, and extends several hundred kilometers to the northeast. The coral-stranatoporoid
reef complex, Emsian in age, occurs in the western Ogilvie Mountains in east-central Alaska.
The algal reef canplex formed a thick barrier that developed along the outer edge of an
east-facing carbonate platform which included coeval ~yclical lagoonal and tidal flat environments, and
deeper-water carbonates containing debris flows. This canplex is a 50Om-thick buildup of predominantly
stromatolitic spongiostromate algal-bound lime and dolomitic mudstone with orbicular, oncolitic and
laminar crusts, abundant irregular fenestrae, and containf' skeletal calcareous algae and sponges
(Aphrosalpinx). Textures indicate periodic subaerial exposure during deposition.
The coral-stranatoporoid reef canplex rims the southwestern end of a carbonate platform which
exhibits a complete suite of depositional environments from basin to shallow water lagoon. The reef is
over 4Om-thick and consists of between 50 ,and 70% ~ ~ and overturned large colonial rugose (notably
Xystriphyllum) and tabulate corals and lesser quantities of massive, tabular and lamellar
stranatoporoids which often cap the corals. Reef interstices are filled with skeletal wackestone to
rudstone matrix and the reef is cored by a Renalcis-bound mudstone.
Spongiostranate stranatolite reefs apparently dominated shelf margin settings in Alaska during
mid-Paleozoic time prior to their ecologic replacement by rugosan-stromatoporoid reef faunas by Emsian
time in east-central alaska, but primarily by Middle Devonian-Frasnian time elsewhere. Following the
terminal Frasnian extinction event, stromatolite buildups were again common on a global scale in the
shelf margin environment during Famennian (late Late Devonian) time.

Conditions of building of a coral reef on a volcanic island can not be easily known, because
the coral coating hides geological contacts. However, in two particular cases, observations have been
made: first on Mururoa, by means of drill holes which have crossed corals and have reached volcanic
bedrock; second, on Rurutu, where a late ell2rsion all OtIS us to observe 110 m -thick coral reef on
submarine lavas.
The two cases are not identical. In the Mururoa case, the coral reef covers (at a depth of
300 m) subaerial lava flows. Deeper, submarine volcanic rocks are found. The aerial volcano of
Mururoa, which had been eroded, is now about 300 m -thick in its central part, and about 100 m -thick
outside. Note that interstratified lill2stone, coral levels have been crossed bet_en aerial lava
flows, as well as between submarine lavas (Gachon et al., this issue).
At Rurutu, reef (late miocene) covers sub~t;;-e volcanism (about 10 m. y. old) without aerial
volcanism between the two levels. That is to say that corals have established themselves on a
submarine plateau, before the emersion of the island. The short gap bet_en the end of volcanism and
the beginning of coral colonisation is due to the pollution of the sea by fine fragments tearing out
the basaltic bedrock.
Although the coral formations are different in these two cases, the relhtion between volcanic
and carbonated rocks are similar. Indeed, at Mururoa, several 10 m -thick alteration levels -
essentially clays -lie between the aerial volcano and the coral reef. Likewise at Rurutu an
interstratified level is to be found. Nevertheless this level seems to be thinner (several m.)
consisting of red clays and manganiferous beds: it was formed in a submarine context.
The t~ studied examples, with their differences and likenesses give us several accurate data
on the growth of corals on a volcano. The geological pattern with the sequence -volcanic bedrock, clay
level, coral reef -may be general.

Mururoa Atoll has been studied by many geophysical surveys either to investigate the structure
of the whole atoll or conversely to study so~ local areas in detail. We describe here funda_ntal
results about the carbonate structure: limestone reef and dolomite.
Two techniques -re used (1) a nultifold high resolution technique ~ich reveals different
zones of volcanism on the atoll, and (2) a high frequency method which investigates, in detail, the
first thirty metres under the lagoon.
The high resolution seismic records show the following main features:
-a regional zone (HRl) extending over the whole lagoon at about 120 metres under the zero hydro. This
zone marks an old erosion surface.
-an unconformity between the top of volcanism and the top of dolomite (HR3 near the summit of the
fossilised volcano).
-a good relationship between the tectonics and the carbonate lithology.
-evident local ananalies of the HR3 zone.
The subsurface exploration of the deposits immediately under the lagoon, with high frequency
seismics, shall variations in carbonate sediment facies near the reef patches and near the sub_rged
reef.

The marine benthic flora of La Reunion has been studied in ST. Gilles reef, from the lagoon to
40 m depth on the outer reef slope, and on the fringing reef of St. Leu. In oodition, observations
have been made in the basaltic zone of Cap La Houssaye.
The ecological distribution of algae species, and the variation of populations in the course
of time, are analysed.
More than 150 species have been recorded with the major part (957.) in coral zones. The
Rhodophyta, which are essentially turfs, are the most abundant in the populations. The sparse
Pheophyta (15% of species) are principally Dictyotales and Fucales. At last, 1/3 of the species are
Chlorophyta and specially Caulerpales.
Seven main algae communities are distinguished: three on the fringing reef, three on the
outer reef slope and one in the basaltic zone.
The whole algal vegetation is widely developed on 58% of the substrata, when corals colonize
only 5%. The flora is the most rich on the outer reef flat. At any locality this zone is
distinguished, at one and the same time, by the high diversity of the species and the high density of
the population. In the other zones, the algal covering is also profuse oot more monotonous and
homogeneous than at the previous locality. The populations are clearly dominated by a few species and
show the characteristics of degradation facies. In these zones the algae have superseded coral
populations.
Finally, variations in algal populations are presented. We distinguish on the one hand, the
variations occurring during the last ten years in relation to coral death and, on the other hand, the
annual seasonal occurrences of the whole algal populations which are a fact of the biological cycles of
the species.